Substrate plating method and apparatus

ABSTRACT

A method and apparatus plate a substrate to form wiring by efficiently filling a fine recess formed in a semiconductor substrate with plating metal without a void or contamination. The plating of the substrate to fill a wiring recess formed in the semiconductor substrate with plating metal includes performing an electroless plating process of forming an initial layer on the substrate, and performing an electrolytic plating process of filling the wiring recess with the plating metal, while the initial layer serves as a feeding layer.

TECHNICAL FIELD

The present invention relates to a method and apparatus for plating asubstrate, and more particularly to a method and apparatus for plating asubstrate to fill a wiring recess formed in a semiconductor substratewith wiring metal such as copper, copper alloy, or the like.

BACKGROUND ART

Conventionally, in order to form a wiring circuit on a semiconductorsubstrate, a layer of Al or Al alloy is deposited on a surface of asubstrate by a sputtering process or the like, and then unnecessaryportions are removed from the layer by a chemical dry etching processusing a photoresist or the like for a mask pattern. However, as thelevel of integration of circuits increases, the width of wiring becomesnarrower to thus increase current density, resulting in generatingthermal stress in the wiring and increasing temperature of the wiring.As a result, the layer of Al or Al alloy becomes thinner due to stressmigration or electromigration, and finally to cause a breaking of thewiring.

Hence, copper has been drawn much attention as a wiring material becauseof its lower resistance and higher reliability. However, it is difficultto form wiring by etching after a layer is deposited on a surface of asubstrate and then performing a patterning process, which is differentfrom a conventional method using Al. Therefore, there has been attempteda damascene process in which a wiring groove is preformed in a substrateand filled with copper by chemical vapor deposition (CVD), sputtering,plating, or the like, and then unnecessary portions are removed from thesurface of the substrate by chemical mechanical polishing (CMP), forthereby forming wiring in the groove.

Among these processes for filling a wiring groove with copper, theplating process has drawn much attention because of the followingadvantages. The processing cost is lower than that in other processes,and pure copper material can be obtained, and the process can beperformed at such a low temperature that a substrate is not damaged. Theplating process mainly comprises an electroless plating process, whichis mainly performed by a chemical process, and an electrolytic platingprocess, which is performed by an electrochemical process. Theelectrolytic plating process is generally more efficient than theelectroless plating process.

Since copper is liable to be oxidized and corroded and diffused intoSiO₂, wiring is generally formed after a wiring portion on a basematerial of the substrate is covered with a barrier layer of metalnitride such as TiN, TaN, and WN. Since the sheet resistance of thisbarrier layer is prohibitively larger than the resistance of the platingliquid, it has been difficult to perform uniform electrolytic plating onthe barrier layer formed over the surface of the substrate.

Conventionally, a seed layer of copper is formed on the barrier layer bya sputtering process or a CVD process, and then plated with copper by anelectrolytic plating process to fill fine recesses formed in thesubstrate with copper. However, it is difficult to uniformly deposit alayer on a wall of the fine recess by the sputtering process, and theCVD process introduces impurities into the deposited layer. Further,when the design rule is further decreased from about 0.18 μm to 0.10 μm,there is no dimensional margin to form a seed layer having a thicknessof 0.02 to 0.05 μm within the recess.

On the other hand, in the electroless plating process, since the platinglayer is grown in isogonic directions from a side wall or a bottomsurface of the fine recess, an inlet of the recess is covered with metalgrown from the side wall and hence, a void tends to be formed in therecess. In addition, since the plating rate of the electroless platingprocess is about one-tenth as slow as that of the electrolytic platingprocess, the electroplating process is inefficient.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodand apparatus for plating a substrate to form wiring by efficientlyfilling a fine recess formed in a semiconductor substrate with platingmetal without a void or contamination.

When formalin (HCHO) is used in the electroless plating process as areducing agent, hydrogen gas (H₂) is generated according to thefollowing reaction.

When a plating surface of a substrate W faces downwardly or sideways, asshown in FIGS. 16A and 16B, bubbles 98 are generated by hydrogen gas(H₂) in a plating liquid Q within recesses 42, such as fine grooves orthe like, formed in the substrate, and these bubbles cause a platingdefect 99. In order to prevent the generation of these plating defects99, a pump or air is generally used to agitate the plating liquid in theconventional plating process. However, as shown in FIG. 16B, unevenlyplated portions 100 are generated on a plating surface 97 of thesubstrate W in the direction that the hydrogen gas bubbles 98 move,indicated by an arrow A.

In order to remove the bubbles 98 from the plating surface 97, theconventional methods employ a jig to grip or suspend the platingsubstrate W, while a shock is applied externally to the jig to separatethe bubbles from the plating surface 97. However, since there is riskthat the shock will damage the jig or the plating substrate, this methodis not desirable.

A conventional electroless plating apparatus comprises a platingprocessing tank and a plating liquid circulating tank, and a platingliquid is circulated during the plating process. The plating liquid isprepared in a special preparation bath or in the circulating tank.Therefore, problematic reactions specific to the electroless copperplating, such as a Cannizzaro reaction or a disproportionation, occur inthe electroless plating liquid immediately after preparation to causedeterioration of the plating liquid and changes in concentration of theplating liquid composition.

Accordingly, it is another object of the present invention to provide amethod and apparatus for electroless plating which can minimize theamount of plating defects and unevenly plated portions and can preventdeterioration of a plating liquid and changes in concentration of theplating liquid composition to perform a plating process with a highlystable quality.

In the conventional electrolytic plating, in order to grow a uniformlayer in through holes formed in a printed circuit board using copperplating, the concentration of copper in the plating liquid is lowered toimprove the throwing power (in a high throwing power bath). This isbecause the overvoltage of a cathode is increased by increasing thepolarization of the cathode to improve the throwing power. A degree ofliquid flow through the holes can be expected when the dimensions of theholes in the printed circuit board are about 50 to 100 μm.

The wiring grooves or holes formed in a surface of a semiconductor waferhave a width or diameter of 0.2 μm or less and do not pass through thesubstrate. Hence, it is impossible to flow a liquid through such finegrooves or holes. Further, the electrophoresis speed generated by theelectric field is numerically small, and hence the holes are filled withcopper ions almost entirely by the diffusion of ion concentration. Theamount of diffusion of copper ions in the holes decreases in proportionto the second power of the hole diameter (the area of the inlet of thehole) as the hole diameter decreases.

In contrast, the amount of deposition of copper ions in the hole growssmaller in proportion to the diameter of the hole. Accordingly, copperions can be expected to be diffusion-controlled in grooves and holes, assemiconductor devices become more integrated and the width of groovesand diameters of holes become smaller in the future. When the holediameters drop below 0.15 μm, in particular, copper ions tend to bediffusion-controlled depending on a methods of agitating plating liquidfor a large aspect ratio.

Therefore, it is another object of the present invention to provide amethod and apparatus of electrolytic plating capable of sufficientlyfilling a fine groove and a hole formed in a surface of a substrateusing a copper plating without copper ions becoming diffusion-controlledin the groove and the hole, even when the width of the groove and thediameter of the hole become smaller and the integration in thesemiconductor devices increases.

According to a first aspect of the present invention, there is provideda method of plating a substrate to fill a wiring recess formed in asemiconductor substrate with plating metal, the method comprising;performing an electroless plating process of forming an initial layer ona substrate; and performing an electrolytic plating process of fillingthe wiring recess with plating metal while the initial layer serves as afeeding layer.

With this method, an initial plating layer (seed layer) is formed withan electroless plating process, and then the recess in the substrate isfilled with electrolytic plating metal while the initial layer serves asthe feeding layer. Accordingly, an electroless plating process with highuniformity is combined with an electrolytic plating process having goodqualities in leveling and high-speed filling. The recess having abarrier layer of a high electrical resistance can efficiently be filledwith a void-free wiring metal, without the sputtering process or the CVDprocess in a series of plating processes. By filling the greatestportion of the recess formed on the feeding layer with the electrolyticplating, it is possible to maintain a high plating speed and increasethroughput.

The electroless plating process and the electrolytic plating process maybe performed in the same plating processing tank or in separateprocessing tanks. Further, the same plating liquid may be used in thesame plating processing tank to perform both of the electroless platingprocess for forming an initial layer serving as a feeding layer and theelectrolytic process for filling the recess. With this method, both ofthe plating processes can continuously be performed without changing theprocessing tank or the plating liquid, for thereby simplifying theapparatus and process while achieving the above effects.

According to a second aspect of the present invention, there is providedan apparatus for plating a substrate to fill a wiring recess in asemiconductor substrate with plating metal, the apparatus comprising: anelectroless plating tank for forming an initial layer on a substrate byelectroless plating; an electrolytic plating tank for filling the wiringrecess with plating metal while the initial layer serves as a feedinglayer; and transfer means for transferring a substrate between thetanks.

With this apparatus, an initial plating layer (seed layer) is formedwith an electroless plating process, and then the recess in thesubstrate is filled with electrolytic plating metal while the initiallayer serves as the feeding layer. Accordingly, the recess having abarrier layer of a high electrical resistance can efficiently be filledwith a void-free wiring metal, without the sputtering process or the CVDprocess in a series of plating processes. The electroless plating tankand the electrolytic plating tank should preferably be disposed in closeproximity to each other within the same space and separated by apartition.

By providing a substrate transfer means in addition to the electrolesstank and the electrolytic plating tank, it is possible to continue fromone process to the next process without changing the state of thesurface of the substrate when transferring the substrate. Specifically,the electroless plating tank, the electrolytic plating tank, andrequired rinse tanks should preferably be arranged in close proximity toeach other, and the substrate should be transferred after the platingprocess or the rinsing process, without exposing the surface of thesubstrate to the air. Such a function may also be provided in thetransfer means itself.

According to a third aspect of the present invention, there is provideda method or apparatus for plating a substrate according to the first orsecond aspect, comprising in the electroless plating process or theelectroless plating bath; means for disposing a substrate to be platedin such a state that a surface to be processed thereof faces upwardly,and forming a hermetically sealed space by the surface to be processed;and plating liquid supply means for supplying an electroless platingliquid to the hermetically sealed space to perform an electrolessplating process.

By facing the plating surface of the substrate to be plated upwardly,nitrogen gas bubbles certainly generated in the plating liquid in theelectroless plating process will moved upwardly due to buoyancy.Accordingly, the number and the amount of bubbles remaining on theplating surface of the plating substrate and in the fine groove and holecan be reduced, thereby reducing the plating defects.

According to a fourth aspect of the present invention, there is provideda method or apparatus for plating a substrate according to the thirdaspect, wherein the minimum amount of electroless plating liquidrequired for performing a predetermined plating on the substrate to beplated is supplied to the hermetically sealed space, and the electrolessplating process is performed with the electroless plating liquid in astatic state. Since this method does not move the nitrogen gas bubblesover the plating surface, it is possible to minimize the unevenly platedportions that are generated on the plating surface, as shown in FIG. 17.

According to a fifth aspect of the present invention, there is provideda method or apparatus for plating a substrate according to the third orfourth aspects, further comprising: pressure pulsation means forgenerating a pressure in the hermetically sealed space that is higherthan atmospheric pressure and for pulsating the pressure.

According to the present invention, since the hydrogen gas bubbles canbe encouraged to dissolve into the electroless plating liquid bypressurization, it is possible to encourage the nitrogen gas bubbles toseparate from the plating surface. Specifically, the nitrogen gasbubbles 98 attached to the plating surface 97 of the plating substrateW, as shown in FIG. 11A, are contracted by pressurization, as shown inFIG. 11B, to separate from the plating surface 97. The nitrogen gasbubbles 98 are expanded by decompression, as shown in FIG. 1C, toseparate completely from the plating surface 97.

According to a sixth aspect of the present invention, there is provideda method or apparatus for plating a substrate according to any one ofthe third through fifth aspects, further comprising a preparation bathdisposed in the vicinity of the hermetically sealed space for supplyingthe minimum amount of prepared electroless plating liquid to thehermetically sealed space just prior to the electroless plating process.

According to the present invention, the plating process is completedbefore an occurrence of problematic reactions specific to theelectroless copper plating, such as a Cannizzaro reaction or adisproportionation, which cause deterioration of the plating liquid andchanges in concentration of the plating liquid composition immediatelyafter the preparation. Therefore, the plating process can be performedwith a highly stable quality.

According to a seventh aspect of the present invention, there isprovided a method or apparatus for plating a substrate according to thesixth aspect, wherein the electroless plating liquid is processed as awaste liquid without circulating the electroless plating liquid afterperforming the electroless plating process with the minimum amount ofelectroless plating liquid.

According to the present invention, since the amount of plating liquidused per deposition (deposition of plating layer) can be maintained tobe the minimum required amount, it is possible to avoid increases incost with the waste liquid and an excessive burden on the environment.

The plating substrate may be held on a turntable in the electrolessplating tank to be rinsed and dried after the plating process. With thisarrangement, the plating, rinsing, and drying processes can all beperformed in the same area, thereby reducing the space required fordevice installation and making the device suitable for installation in aclean room.

A hot bath for maintaining temperature may be provided in theelectroless plating tank in the vicinity of the top of the hermeticallysealed space, and a heater for maintaining temperature may be disposedbelow the plating substrate. With this arrangement, it is possible tomaintain a fixed plating temperature, which is one of the most importantfactors governing the quality (uniformity of layer thickness,reproducibility, electric conductivity of the plating layer, etc.) ofelectroless plating.

In the electroless plating process, the minimum required amount ofelectroless plating liquid may be set within a range of amount of liquidthat includes ions of solutes 1.5 to 20 times as many as a predetermineddeposited metal equivalent. In the electroless plating process, thepressure pulsation means may be configured to generate pressurepulsations having an amplitude of 0 to 1 MPa and a frequency of 0 to 10Hz.

According to an eighth aspect of the present invention, there isprovided a method or apparatus for plating a substrate according to thefirst or second aspects, wherein the plating liquid used in theelectroless plating process or the electroless plating bath comprisescopper sulfate (CuSO₄.5H₂O) having a concentration of 100 to 250 g/l,sulfuric acid (H₂SO₄) having a concentration of 10 to 100 g/l, andchlorine ions having a concentration of 0 to 100 mg/l.

According to a ninth aspect of the present invention, there is provideda method or apparatus for plating a substrate according to the eighthaspect, wherein the electrolytic plating liquid further comprises atleast 0.14 to 70 μmol/l of a sulfur compound expressed by a formula [A]below, 10 to 5000 mg/l of a macromolecular compound expressed in aformula [B] below, and 0.01 to 100 mg/l of a nitrogen compound; whereinL is an alkyl group having a carbon number of 1 to 6 which issubstituted by a lower alkyl group, a lower alkoxyl group, a hydroxylgroup, or a halogen atom; and X is a hydrogen atom, a —SO₃M group, or a—PO₃M group (M indicating a hydrogen atom, an alkali metal atom, or anamino group) in the formula [A]; and R₁ indicates a residue of a higheralcohol group having a carbon number of 8 to 25, a residue of an alkylphenol with an alkyl group having a carbon number of 1 to 25, a residueof an alkyl naphthol with an alkyl group having a carbon number of 1 to25, a residue of a fatty acid amide having a carbon number of 3 to 22, aresidue of an alkylamine having a carbon number of 2 to 4, or a hydroxylgroup; R₂ and R₃ indicate a hydrogen atom or a methyl group; and m and kindicate an integer from 1 to 100 in the formula [B],X—L—(S)_(n)—L—X  [A]

Since increases in copper concentration in the plating liquid generateproportional increases in the diffusion speed, it is possible to preventcopper ions from becoming diffusion-controlled in the groove and thehole, even when the width of the groove and the diameter of the holebecome smaller and the integration in the semiconductor devicesincreases. Of course, it is also possible to produce a thinner diffusionlayer and suppress the current density by agitating the plating liquid.

FIG. 18 is a graph comparing diffusion amount and deposition amount in ahole H of 2.2 μm shown in FIG. 19. In FIG. 18, the vertical axisrepresents the amount of copper deposition and the amount of copperdiffusion (g/s), and the horizontal axis represents the diameter φ (μm)of the hole H. Here, the diffusion coefficient is set at 0.72×10⁻⁹ m²/sand the diffusion layer thickness at 5 μm. When the diffusion amount isgreater than the deposition amount, the ions become reaction-controlledto prevent a depletion in copper ions in the hole H and the generationof voids therein. When the diffusion layer is less than the depositionamount, the ions become diffusion-controlled, and voids are generated inthe hole H. As seen in FIG. 18, higher concentrations of copper sulfateare advantageous when the hole diameter becomes finer, while thesulfuric acid concentration relatively declines due to the relationshipwith saturated concentration. By reducing the sulfuric acidconcentration, the electrical resistance of the plating liquidincreases, improving the uniformity of the deposited layer thickness.

In FIG. 18, a curve A indicates the diffusion amount (per second) whenthe copper sulfate concentration is 225 g/l, a curve B indicates thedeposition amount (per second) when the current density is 3 A/dm², acurve C indicates the deposition amount (per second) when the currentdensity is 2.5 A/dm², a curve D indicates the deposition amount (persecond) when the current density is 2 A/dm², and a curve E indicates thediffusion amount (per second) when the copper sulfate concentration is75 g/l.

As described above, the plating liquid includes the sulfur compoundshown in equation [A] of 0.14 to 40 μmol and the macromolecular compoundshown in equation [B]. This sulfur compound can achieve a finedeposition. Some examples of these compounds include N,N-dimethyldithiocarbamylpropylsulfonic acid, O-ethyl-S-(3-propylsulfonicacid)-dithiocarbonate, bis-(sulfopropyl) disulfide, and their salts.

In the present invention, the amount of additive in the sulfur compoundshould preferably be 0.14 to 70 μmol/l, since the amount of coppersulfate is greater than the amount of sulfuric acid. The amount ofadditive in the sulfur compound is less than that in the case where asolution with a low concentration of copper sulfate is used because thecathode vicinity is rich in copper ions, requiring less sulfur compoundas an accelerating agent.

Some examples of a macromolecular organic additive contained in theplating liquid are PPG and PEG, their random or block polymers, or aderivative thereof, such as a polyether type. The amount ofmacromolecular organic additive is about 10 to 5000 mg/l.

A leveler is added to the above plating liquid to further control thecopper deposition and accelerate plating growth in the bottom of thehole. The leveler is a nitrogen compound containing a polyalkyleneimine, such as a phenazine compound, a phthalocyanine compound, apolyethylene imine, and a polybenzyl ethylene imine, or a derivativethereof, or a thiourea derivative such as an N-dye substitute compound,a safranine compound, such as a phenosafranine, a safranine azonaphthol, a diethyl safranine azo phenol, and a dimethyl safraninedimethyl aniline, or a polyepichlorohydrine or a derivative thereof, ora phenylthiazonium compound such as a thioflavine, or a amide type, suchas an acrylamide, a propylamide, and a polyacrylic acid amide. Thisnitrogen compound of about 0.01 to 100 mg/l is added as a leveler.

According to the present invention defined in a tenth aspect, there isprovided an apparatus for plating a substrate to fill a wiring recessformed in a semiconductor substrate with plating metal, the apparatuscomprising: one processing tank having an electroless plating liquidsupply path for supplying an electroless plating liquid to form aninitial layer on a substrate by an electroless plating process, and anelectrolytic plating liquid supply path for supplying an electrolyticplating liquid to fill the wiring recess by electrolytic plating whilethe initial layer serves as a feeding layer; wherein the two paths areselectively switchable.

Hence, an initial plating layer (seed layer) is formed with anelectroless plating process, and then the recess in the substrate isfilled with electrolytic plating metal while the initial layer serves asthe feeding layer. Accordingly, the recess having a barrier layer of ahigh electrical resistance can efficiently be filled with a void-freewiring metal, without the sputtering process or the CVD process in aseries of plating processes. Since both of the electroless platingprocess for forming the initial layer and the electrolytic platingprocess for filling the recess can be performed continuously in the sameprocessing tank, the equipment and time required to transfer thesubstrate can be minimized and the state of the surface of the substratecan be prevented from changing. A cleaning liquid supply path forcleaning a substrate may be disposed to perform a cleaning process inthe same processing tank.

The processing tank may be hermetically sealed with a parallel flow.With this arrangement, a plating liquid can flow along the surface ofthe substrate at a high speed even in a small space to thus perform theefficient plating with sufficient flowability of the plating liquid.

According to an eleventh aspect of the present invention, there isprovided a method or apparatus for plating a substrate according to anyone of the first through tenth aspects, wherein the plating liquid usedin the method or apparatus does not include an alkali metal as a pHregulator.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view showing a whole structure of a plating apparatusaccording to a first embodiment of the present invention;

FIG. 2 is a side view showing a processing tank used in the platingapparatus of FIG. 1;

FIG. 3 is a cross-sectional view taken along a line A—A of theprocessing tank in FIG. 2;

FIG. 4 is a schematic view showing the processing tank used in theplating apparatus in FIG. 1 and circulating paths of a processingliquid;

FIG. 5 is a side view of the plating apparatus in FIG. 1;

FIG. 6 is a flowchart showing processes performed with the platingapparatus in FIG. 1;

FIGS. 7A through 7D are schematic diagrams explanatory of a process ofplating a recess formed in a substrate;

FIG. 8 is a schematic view showing a processing tank used in a platingapparatus according to a second embodiment of the present invention;

FIG. 9 is a plan view showing a whole structure of a plating apparatusaccording to a third embodiment of the present invention;

FIG. 10 is a schematic view showing a structure of an electrolessplating device in FIG. 9;

FIGS. 11A through 11C are schematic diagrams explanatory of the behaviorof hydrogen gas bubbles when pressure of a hermetically sealed space inthe electroless plating device is pulsed;

FIG. 12 is a schematic view showing a structure of the electrolessplating device in FIG. 9;

FIG. 13 is a schematic view showing a structure of an electrolyticplating device in FIG. 9:

FIG. 14 is an enlarged view of an area B indicated in FIG. 13;

FIG. 15 is a schematic view showing a processing tank used in theplating apparatus and circulating paths of a processing liquid accordingto the third embodiment of the present invention;

FIGS. 16A and 16B are schematic diagrams explanatory of the behavior ofhydrogen gas bubbles in electroless plating, FIG. 16A shows the behaviorof the hydrogen gas bubbles when a plating surface of a platingsubstrate faces downwardly, and FIG. 16B shows the behavior of thehydrogen gas bubbles when the plating surface of the plating substratefaces sideways;

FIG. 17 is a schematic diagram explanatory of unevenly plated portionsgenerated on a plating surface of a plating substrate by the behavior ofhydrogen gas bubbles in electrolytic plating;

FIG. 18 is a graph comparing diffusion amount and deposition amount inholes formed in a plating substrate; and

FIG. 19 is a schematic view showing an example of a shape of a holeformed in a surface of a plating substrate.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments according to the present invention will be described belowwith reference to the accompanying drawings. A plating apparatus isdisposed in a rectangular installation frame 10, as shown in FIG. 1. Theplating apparatus has a clean zone 13 at one side of the installationframe 10, and load/unload units 14 a, 14 b and two cleaning and dryingdevices 60 for post-processing a substrate, after the plating process,are disposed at the clean zone 13. A transfer device (first transferrobot) 61 for transferring a substrate is provided among the load/unloadunits 14 a, 14 b and the cleaning and drying devices 60. The platingapparatus has a contaminated zone 12 at the other side of theinstallation frame 10, and a second transfer robot 62 movable on a railis disposed at the central portion of the contaminated zone 12. An SnCl₂solution tank 16 containing SnCl₂ solution used as an activator inplating, a rinse tank 17, a PdCl₂ solution tank 18 containing Pdcl₂solution used as a catalyst in electroless plating, and a rinse tank 19are disposed in order on one side with respect to the second transferrobot 62. An electroless plating tank 20, a rinse tank 21, anelectrolytic plating tank 22, and a rinse tank 23 are disposed in orderon the other side with respect to the second transfer robot 62. Therinse tanks 11, 19, 21 and 23 may be provided as needed.

Each of these processing tanks 16–23 has the same basic shape andstructure, and comprises a processing container body 50 having arectangular plate shape and a recess 50 a forming a processing chamber52 therein, and a cover 51 capable of opening and closing a frontopening of the processing container body 50, as shown in FIG. 2. Apacking 53 is mounted at the peripheral portion of the processingcontainer body 50 to maintain the water-tightness of the processingcontainer body 50 when the cover 51 is closed and brought into closecontact with the processing container body 50. A holding member fordetachably holding a substrate W is provided on the inner side of thecover 51, and the cover 51 is provided with a sensor (not shown) fordetecting the existence of a substrate W on the holding member.

In the processing tank (electrolytic plating tank) 22 for performingelectrolytic plating, a plate-like anode 54 is mounted on the bottom ofthe recess 50 a in the processing container body 50 in parallel with theprocessing chamber 52, and a shielding plate 55 made of dielectricmaterial is disposed at the opening end of the recess 50 a. Theshielding plate 55 has an opening 55 a therein for regulating theelectric field on a plating surface of the substrate W. The otherprocessing tanks are not provided with the anode 54 or the shieldingplate 55.

An upper header 56 and a lower header 57 are mounted on the top andbottom of the processing container body 50 and communicate with theprocessing chamber 52 via a plurality of through-holes 56 a, 57 a,respectively. Thus, for example, a processing liquid is supplied fromthe lower header 57 to the upper header 56 to thus generate a parallelflow along the surface of the substrate to be plated, as shown in FIG.3. As shown in FIG. 4, processing liquid circulating devices 33 eachhaving a reservoir tank 31 and a circulating pump 32 are provided belowthe processing tanks 16–23, and a supply pipe 34 and a return pipe 35extending from the processing liquid circulating device 33 are connectedto the lower header 57 and the upper header 56.

Since, as described above, the plating tanks 20, 22 are hermeticallysealed with a parallel flow, a plating liquid can flow along the surfaceof the substrate at a high speed even in a small space to thus performthe efficient plating with sufficient flowability of the plating liquid.Further, each of the processing tanks 16–23 is vertically positioned,and hence bubbles in fine recesses formed in the substrate W can easilyflow out therefrom during the plating process or the like. Therefore,uniformity of the plating reaction and the processing rate can beincreased, and simultaneously the installation area of the processingtanks 16–23 can be reduced, resulting in an efficient arrangement of theprocessing tanks.

In this embodiment, the transfer robot 62 comprises a hexaxial robothaving a plurality of arms 63 and a hand 64 which is provided on the endof the arms 63 and is capable of opening and closing (see FIG. 5). Aplurality of rollers 65 are rotatably supported on the inner surface ofthe hand 64. A temporary holding stage 66 having a plurality of supportsis provided in the clean zone 13 and used for temporarily holding asubstrate W to be transferred between the clean zone 13 and thecontaminated zone 12.

Next, the plating process according to the plating apparatus thusconstructed will be described below with reference to FIGS. 6 and 7. Thefirst transfer robot 61 takes out a substrate W held on the load/unloadunit 14 a, 14 b and places the substrate W on the temporary holdingstage 66. The second transfer robot 62 transfers the substrate W to thecontaminated zone 12, and, when necessary, the substrate W is insertedinto the processing container body 50 of the activation tank 16 andactivated by a processing liquid containing an activator such as SnCl₂.Next, the substrate W is transferred to the adjacent rinse tank 17 to berinsed, and then transferred to the catalyst application tank 18 toreceive a catalyst application.

In this process, Sn²⁺ ions from the activator are adsorbed by thesurface of the substrate W in the activation tank 16, and these ions areoxidized in the catalyst application tank 18 to be Sn⁴⁺. On the otherhand, Pd²⁺ ions are reduced to Pd metal, and the Pd metal is depositedon the surface of the substrate W to serve as a catalyst in thefollowing electroless plating process. A single catalyst containingPd/Sn colloids may be used in this process. In this embodiment, thecatalyst application process described above is performed in theactivation tank 16 and the catalyst application tank 18 belonging to aportion of the plating apparatus. However, the catalyst applicationprocess may be performed in a separate apparatus, and then the substrateW may be transferred to the plating apparatus. It is possible todispense with the activation process and/or the catalyst applicationprocess in some cases, depending on a material or a state of the innersurface of the recess formed in the semiconductor substrate.

The second transfer robot 62 further transfers the substrate W to theelectroless plating tank 20, where the electroless plating process isperformed with a predetermined reducing agent and a predeterminedplating liquid. With this process, as shown in FIGS. 7A and 7B, anelectroless plating layer 41 is formed on the inner surface of a barrierlayer 40. In this case, electrons generated at the solid-liquidinterface due to decomposition of the reducing agent are applied to theCu²⁺ via the catalyst on the surface of the substrate, and hence Cumetal is deposited on the catalyst to form the copper layer 41. Inaddition to Pd, other transition metals such as Fe, Co, Ni, Cu, and Agmay be used as the catalyst.

Next, the substrate W is transferred to the electrolytic plating tank 22by the transfer robot, and the copper layer 41 formed by the electrolessplating process is connected to an electrode to perform the electrolyticplating process with a predetermined plating liquid, for thereby fillingthe recess 42 with electrolytic plating metal 43, as shown in FIGS. 7Cand 7D.

After the electrolytic plating process is completed, the substrate istaken out by the second transfer robot and transferred to the rinse tankto be rinsed and then placed on a second temporary holding stage 67. Thesubstrate is held by the first transfer robot 61 and transferred to thecleaning and drying device 60 to be cleaned and dried for finishing, andreturned to the load/unload unit 14 a, 14 b. The substrate is finallytransferred to a chemical mechanical polishing apparatus (CMP) to removeunnecessary plating metal from the surface of the substrate with thechemical mechanical polishing process.

FIG. 8 shows a plating apparatus according to another embodiment of thepresent invention. The plating apparatus comprises a vertical processingtank 24 as in the previous embodiment, and processing liquid circulatingdevices 33 a, 33 b, 33 c for circulating and supplying a respectiveprocessing liquid (electroless copper plating liquid, rinse water, andelectrolytic copper plating liquid) to the processing tank 24. Supply ofthe processing liquid can be switched by switching valves 36 a through36 c and 37 a through 37 c. The processing tank 24 comprises aprocessing container base 50 having an anode 54 and a shielding plate 55therein, as in the example shown in FIG. 2, and can perform theelectrolytic plating process.

In this embodiment, for example, after the electroless plating processis completed, the plating liquid is returned to the reservoir tank 31 a.A rinse water circulating pump 32 b is operated to introduce rinse waterinto the processing tank 24, and then an electrolytic plating liquid isintroduced from the reservoir tank 31 c into the processing tank 24.After the electrolytic plating process is completed, a rinsing processis similarly performed. Thus, it is possible to eliminate such problemsthat plating liquids are mixed with each other. In this embodiment, theelectroless copper plating process, the rinsing process, theelectrolytic copper plating process, the rinsing process, and otherprocesses can be continuously performed in the same processing tank 24without transferring a substrate, simply by changing processing liquids.Therefore, the present embodiment can decrease the number of therequired tanks compared with the previous embodiment and can eliminatethe need of a transfer robot for transferring a substrate between tanks,for thereby compacting a installation frame. Further, throughput isincreased as the transferring time can be eliminated.

FIG. 9 shows a plating apparatus according to still another embodimentof the present invention, A transferring rail 61 a is extended from oneside of a rectangular frame to the other side of the frame, and atransfer device (transfer robot) 61 is movably provided on thetransferring rail 61 a. A load/unload unit 41, a pre-treatment unit 68,an electroless plating unit 69, a first spin drying unit 70A, anelectrolytic plating unit 71, and a second spin drying unit 70B areclockwise disposed in order so that these units surround the transferrobot 61. The pre-treatment unit 68 comprises an activator (SnCl₂solution) tank or a catalysis (PdCl₂ solution) tank, for example.

FIG. 10 is a schematic view showing a configurational example of theelectroless plating unit 69 shown in FIG. 9. The electroless platingunit 69 has a turntable 72 for holding a substrate W to be plated suchas a semiconductor substrate thereon. A heater 73 for maintainingtemperature is provided in the turntable 72, and the turntable 72 can bemoved vertically via a ball screw 85 by a motor 86 and rotated via atiming belt 83 by a motor 84.

A plating cell 92 having an opening in its lower surface is disposedabove the turntable 72, and a seal packing 91 which is brought intoclose contact with the plating substrate W held by a housing 96 isprovided at the outer edge of the lower end of the plating cell 92.Specifically, when the turntable 72 is upwardly moved, a hermeticallysealed space is formed in the plating cell 92 in such a state that thesurface of the plating substrate W is brought into close contact withthe seal packing 91. The hermetically sealed space has a volumesufficient for accommodating the minimum amount of plating liquid(electroless plating liquid) required for performing a predeterminedplating on the surface of the plating substrate W, as described later.

A preparation bath 74 is disposed in the vicinity of the upper portionof the plating cell 92 and supplied with plating liquids A, B, C, andpure water D. An impeller 76 a connected to an agitator 76 is disposedin the preparation bath 74, and a heater 81 is disposed in thepreparation bath 74. A plating liquid in the preparation bath 74 issupplied to the plating cell 72 via a plating liquid supply valve 79.

A hot bath 75 is disposed in the vicinity of the outer portion of thepreparation bath 74 so as to surround the preparation bath 74. Animpeller 77 a connected to an agitator 77 is disposed in the hot bath75, and a heater 82 is disposed in the hot bath 75. The referencenumeral 80 denotes a plating liquid discharge valve for discharging aplating liquid after the plating process is completed in the platingcell 92. A plating liquid discharged through the plating liquiddischarge valve 80 flows into a waste liquid tank 93. The referencenumeral 78 denotes a pressure supply valve for supplying pressure intothe plating cell 92. The pressure in the plating cell 92 can be pulsedvia the pressure supply valve 78 by a pressure pulsation generator 94.

The pressure pulsation generator 94 comprises a pressure regulator valve87 for high pressure, a pressure regulator valve 88 for low pressure, aswitching valve 89 for switching pressure, and a pneumatic pressuresource 90, and can generate pressure pulsations having an amplitude of 0to 1 MPa and a frequency of 0 to 10 Hz. The reference numerals P1, P2denote pressure gauges.

In the electroless plating apparatus thus constructed, when a substrateW is plated, the plating substrate W is held in a predetermined positionon the upper surface of the turntable 72 positioned below the platingcell 92. In this state, the turntable 72 is moved upwardly via the ballscrew 85 by the motor 86 to thus bring the upper surface of the platingsubstrate W into close contact with the seal packing 91, thereby closingthe lower opening of the plating cell 92 to form a hermetically sealedspace therein. At this time, the supply valve 79 is opened to supply theplating liquid Q in the preparation bath 74 to the plating cell 92.

The interior of the plating cell 92 has a volume sufficient foraccommodating the minimum amount of plating liquid Q required forperforming a predetermined plating on the surface of the platingsubstrate W, and this minimum required amount of plating liquid Q isaccommodated in the interior of the plating cell 92. Here, the minimumrequired amount of electroless plating liquid is set within a range ofamount of liquid that includes ions of solutes 1.5 to 20 times as manyas a predetermined deposited metal equivalent. In the plating process,the pressure pulsation generator 94 applies a pressure pulsation to theplating cell 92 via the pressure supply valve 78 at a predeterminedamplitude and a predetermined frequency.

As shown in FIGS. 11A through 11C, since the plating substrate W is heldon the upper surface of the turntable 72 in such a state that thesurface to be plated faces upwardly, hydrogen gas bubbles 98 certainlygenerated in the plating liquid Q in the electroless plating process aremoved upwardly due to buoyancy. Therefore, the number and the amount ofbubbles remaining on the plating surface 97 of the plating substrate Wand in fine grooves and holes are reduced, for thereby reducing theplating defects. Further, the minimum required amount of plating liquidQ is supplied to the hermetically sealed space in the plating cell 92,and the substrate is plated in a stationary state. Hence, the hydrogengas bubbles 98 are not moved on the plating surface 97, therebyminimizing the amount of unevenly plated portions generated on theplating surface.

The pressure of the hermetically sealed space in the plating cell 92 isset to be higher than atmospheric pressure and pulsed by the pressurepulsation generator 94. Hence, as described above, the hydrogen gasbubbles 98 can be encouraged to dissolve into the electroless platingliquid Q by pressurization and simultaneously encouraged to separatefrom the plating surface 97 by pressure pulsation, as shown in FIGS. 11Athrough 11C.

The preparation bath 74 is disposed in the vicinity of the upper portionof the plating cell 92, and the minimum required amount of platingliquid prepared in the preparation bath 74 is supplied to the platingcell 92 just before the substrate W is plated. Hence, the platingprocess is completed before the occurrence of problematic reactionsspecific to the electroless copper plating, such as a Cannizzaroreaction or a disproportionation, which cause deterioration of theplating liquid and changes in concentration of the plating liquidcomposition after the preparation. Therefore, the plating process can beperformed with a highly stable quality.

The plating liquid Q used for plating is discharged from the platingcell 92 via the plating discharge valve 80 into the waste liquid tank93, where the plating liquid Q is processed as a waste liquid. Hence,the plating process can be performed with a highly stable quality. Inaddition, since the amount of plating liquid used per deposition ismaintained to be the minimum required amount, it is possible to avoidincreases in cost with the waste liquid and an excessive burden on theenvironment. Further, since the hot bath 75 is disposed above theplating cell 92 and the heater 73 for maintaining temperature isdisposed below the turntable 72, it is possible to maintain a fixedplating temperature, which is one of the most important factorsgoverning the quality uniformity of layer thickness, reproducibility,electric conductivity of the plating layer, etc.) of electrolessplating.

After the plating process is completed, as described above, the platingliquid discharge valve 80 is opened to discharge the plating liquid inthe plating cell 92 to the waste liquid tank 93. The turntable is moveddownwardly via the ball screw 85 by the motor 86, and a cleaning liquid(mainly pure water) is ejected from a cleaning nozzle 95 shown in FIG.12 to the plating surface of the plating substrate W to clean theplating surface. In this cleaning process, a cleaning nozzle 95 isswung, and the plating substrate W is slowly rotated via the timing belt83 by the motor 84. After the cleaning process is completed, the platingsubstrate W is rotated at a high speed to spin off the cleaning liquidattached to the plating substrate X by centrifugal force.

After a seed layer is formed on the barrier layer in the wiring groovesby the electroless plating process, the substrate W is transferred tothe first spin drying unit 70A by the transfer robot 61 and completelydried therein. Then, the substrate W is transferred to the electrolyticplating unit 71, where the electrolytic plating process is performed.The electrolytic plating process will be described below with referenceto FIGS. 13 and 14.

As shown in FIG. 13, the electrolytic plating unit 71 comprises aplating tank 110, and the plating tank 110 comprises a plating tank body111 and a substrate holding member 112 for holding a plating substrate Wsuch as a semiconductor substrate in the plating tank body 111. Thesubstrate holding member 112 has a substrate holding portion 112-1 and ashaft portion 112-2, and the shaft portion 112-2 is rotatably supportedin an inner wall of a cylindrical guide member 114 via bearings 115,115. The guide member 114 and the substrate holding member 112 arevertically movable at a predetermined stroke by a cylinder 116 providedon the top of the plating tank body 111.

The substrate holding member 112 is rotated in a direction indicated bythe arrow A via the shaft portion 112-2 by a motor 118 provided on theinner side of the upper portion of the guide member 114. A space C isformed in the substrate holding member 112, and a substrate pressermember 1117 having a substrate presser portion 117-1 and a shaft portion117-2 is accommodated in the space C. The substrate presser member 117is vertically movable at a predetermined stroke by a cylinder 119provided on the top of the shaft portion 112-2 in the substrate holdingmember 112.

An opening 112-1 a communicating with the space C is formed below thesubstrate holding portion 112-1 of the substrate holding member 112,and, as shown in FIG. 14, a step portion 112-1 b on which the peripheralportion of the plating substrate W is placed is formed at the upperportion of the opening 112-1 a. The peripheral portion of the platingsubstrate W is placed on the step portion 112-1 b, and the upper surfaceof the plating substrate W is pressed by the substrate presser portion117-1 of the substrate presser member 117, for thereby clamping theperipheral portion of the plating substrate W between the substratepresser portion 117-1 and the step portion 112-1 b. The lower surface(plating surface) of the plating substrate W is exposed to the opening112-1 a, FIG. 14 is an enlarged view of the area B indicated in FIG. 13.

A flat plating liquid chamber 120 is provided below the substrateholding portion 112-1 of the plating tank body 111, i.e., below theplating surface of the plating substrate W exposed to the opening 112-1a, and a flat plating liquid introduction chamber 122 is provided belowthe plating liquid chamber 120 via a perforated plate 121 having a largenumber of holes 121 a. The recovery gutter 123 for recovering a platingliquid Q overflowing the plating liquid chamber 120 is provided outsideof the plating liquid chamber 120.

The plating liquid Q recovered in the recovery gutter 123 is returned toa plating liquid tank 124. The plating liquid Q in the plating liquidtank 124 is horizontally introduced to the plating liquid chamber 120from both sides thereof by a pump 125. The plating liquid Q introducedto the plating liquid chamber 120 from both sides thereof flowsvertically into the plating liquid chamber 120 through the holes 121 aformed in the perforated plate 121. A distance between the perforatedplate 121 and the plating substrate W is set to be 5 to 15 mm. The flowof the plating liquid Q passed through the holes 121 a formed in theperforated plate 121 is brought into contact with the plating surface ofthe plating substrate W in such a state that the plating liquid Q flowsupwardly as a uniform flow. The plating liquid Q overflowing the platingliquid chamber 120 is recovered in the recovery gutter 123 and flowsinto the plating liquid tank 124. Specifically, the plating liquid Q iscirculated between the plating liquid chamber 120 in the plating tankbody 111 and the plating liquid tank 124.

The plating liquid level L_(Q) in the plating liquid chamber 120 ishigher than the plating surface level L_(W) of the plating substrate Wby a slight distance ΔL, and the plating liquid Q is brought intocontact with the whole surface of the plating substrate W.

An electrical contact 127 for electrically connecting with a connectingportion of the plating substrate W is provided in the step portion 112-1b of the substrate holding portion 112-1 in the substrate holding member112. The electrical contact 127 is connected to a cathode of an externalplating power supply (not shown) via a brush 126. An anode 128 isprovided on the bottom of the plating liquid introduction chamber 122 inthe plating tank body 111, in confrontation with the plating substrateW. The anode 12B is connected to an anode of the plating power supply. Atransfer slit 129 for inserting and removing the plating substrate Wwith a substrate transfer jig such as a robot arm is formed at apredetermined position in the wall of the plating tank body 111.

When the plating process is performed in the electrolytic plating unitthus constructed, the substrate holding member 112 is moved upwardly toa predetermined position (a position at which the plating substrate Wheld by substrate holding portion 112-1 opposes the transfer slit 129)together with the guide member 114 by actuating the cylinder 116, andsimultaneously the substrate presser member 117 is moved upwardly to apredetermined position (a position at which the substrate presserportion 117-1 reaches the upper portion of the transfer slit 129) byactuating the cylinder 119. In this state, the plating substrate W istransferred to the space C in the substrate holding member 112 by thesubstrate transfer jig such as a robot arm and placed on the stepportion 112-1 b in such a state that the plating surface of the platingsubstrate W faces downwardly. At this state, the substrate presserportion 117-1 is moved downwardly to a position at which the lowersurface of the substrate presser portion 117-1 is brought into contactwith the upper surface of the plating substrate W, by actuating thecylinder 119, and hence the peripheral portion of the plating substrateW is clamped between the substrate presser portion 117-1 and the stepportion 112-1 b.

In this state, the substrate holding member 112 is moved downwardly to aposition at which the plating surface of the plating substrate W isbrought into contact with the plating liquid Q in the plating liquidchamber 120 (a position ΔL lower than the plating liquid level L_(Q))together with the guide member 114 by actuating the cylinder 116. Whilethe substrate holding member 112 is being moved downwardly, thesubstrate holding member 112 and the plating substrate W are rotated ata low speed by actuating the motor 118. The plating liquid chamber 120is filled with the plating liquid Q, and the plating liquid passedthrough the holes 121 a formed in the perforated plate flows verticallyupwardly in the plating liquid chamber 120. In this state, when apredetermined voltage is applied between the anode 128 and the electriccontact 127 by the plating power supply, a plating current flows fromthe anode 128 to the plating substrate W to form the plating layer onthe plating surface of the plating substrate W.

During the plating process, the substrate holding member 112 and theplating substrate W are rotated at a low speed by actuating the motor118. This rotation at a low speed is set such that the vertical flow ofthe plating liquid Q in the plating liquid chamber 120 is notinterrupted, and a plating layer having a uniform thickness can beformed on the plating surface of the plating substrate W.

When the plating process is completed, the substrate holding member 112and the plating substrate W are moved upwardly by actuating the cylinder116. When the lower surface of the substrate holding portion 112-1 ispositioned above the plating liquid level L_(Q), the motor 118 rotatesthe substrate holding member 112 and the plating substrate W at a highspeed to spin off the plating liquid attached on the plating surface ofthe plating substrate W and the lower surface of the substrate holdingportion 1121. After the plating liquid is spun off, the platingsubstrate W is moved upwardly to a position corresponding to thetransfer slit 129. When the substrate presser portion 117-1 is movedupwardly by actuating the cylinder 119, the plating substrate W isreleased from the substrate presser portion 117-1 in such a state thatthe plating substrate W is placed on the step portion 112-1 b of thesubstrate holding portion 112-1. In this state, the substrate transferjig such as a robot arm is inserted from the transfer slit 129 into thespace C in the substrate holding member 112 to pick up the platingsubstrate W and transfer it to the exterior.

With the electrolytic plating unit 71 thus constructed, a platingsubstrate N in which holes having a diameter of 0.15 μm and a depth of1.2 μm were formed was plated by the electrolytic plating process tofill the holes with copper. A plating liquid Q having the followingcomposition, a current density of 2 A/dm², and a temperature of 25° C.was used, and a plating time was set to 150 seconds. The holes wereefficiently filled with copper.

Composition of Plating Liquid Q

CuSO₄.5H₂O 225 g/l H₂SO₄ 55 g/l Cl⁻ 60 mg/l Sulfur compound(N,N-dimethyldithiocarbamylpropyl- 5 mg/l sulfonic acid) Macromolecularcompound (PEG6000) 0.1 g/l Nitrogen compound (safranine compound, janusgreen B) 2 mg/l

When a plating liquid having a high concentration of copper sulfate(CuSO₄.5H₂O) is used, as described above, a hole having a diameter of0.15 μm and a depth of 1.2 μm can efficiently be filled with copper byplating.

FIG. 15 shows a processing tank 25 which can continuously perform anelectroless plating process and an electrolytic plating process with thesame processing liquid. The processing tank 25 can perform anelectrolytic plating process as with the processing tank shown in FIG.8. In this processing tank, the electroless plating process isperformed, and then the electrolytic plating process is directlyperformed by energization of a low current of less than 0.2 A/dm². Inthis case, an electroless plating liquid is used as a plating liquid,and TMAH is used in place of NaOH or KOH usually used as a pH regulatorin the electroless plating process, in order to prevent thesemiconductor substrate from being contaminated. TMAH is an organicalkali chemical including a methyl group. It is necessary to avoid usinga reducing agent liable to be decomposed, such as formalin, which hascommonly been used.

Conventionally, in the through hole plating of the printed circuitboard, throwing power has been improved by a high throwing power bath(CuSO₄.5H₂O 10–80 g/l) having a low Cu concentration. However, whentrenches and via holes of a semiconductor substrate are plated, not onlythrowing power but also leveling of plating is required in order toprevent the generation of voids. Further, since the high throwing powerbath is easily influenced by the flow of a plating liquid, it isdesirable to use a plating liquid having a mid to high increasedconcentration for reducing the possibility of flow effects.

Various things were examined under the above preconditions. As a result,conventionally used baths such as a CuSO₄.5H₂O low concentration (15–80g/l) bath (high throwing power bath) superior in throwing power, or aCuSO₄.5H₂O high concentration (150–220 g/l) bath (decorative bath)superior in leveling of plating were found not to be appropriate. ACuSO₄.5H₂O mid concentration (100–150 g/l) bath was found to beappropriate for a damascene plating process which combines anelectroless plating process and an electrolytic plating process of asemiconductor substrate.

As described above, according to the present invention, an initialplating layer (seed layer) is formed with an electroless platingprocess, and then the recess in the substrate is filled withelectrolytic plating metal while the initial layer serves as the feedinglayer. Accordingly, the recess having a barrier layer of a highelectrical resistance can efficiently be filled with a void-free wiringmetal, without the sputtering process or the CVD process in a series ofplating processes. Therefore, the present invention can provide a methodand apparatus for plating a substrate to form wiring by efficientlyfilling a fine recess formed in a semiconductor substrate with platingmetal without a void or contamination.

INDUSTRIAL APPLICABILITY

The present invention is suitable for a method and apparatus for platinga substrate to fill a wiring recess formed in a semiconductor substratewith wiring metal such as copper, copper alloy, or the like.

1. An apparatus for plating a surface of a substrate to fill a wiringrecess in the surface with a metal, said apparatus comprising: a frame;a load/unload unit on which the substrate is held; a transfer mechanismdisposed in said frame; and a plurality of processing units disposed insaid frame so as to surround said transfer mechanism, said processingunits including: an electroless plating unit for performing anelectroless plating process to form an initial layer on the substrate;and an electrolytic plating unit for performing an electrolytic platingprocess to fill the wiring recess with the metal while the initial layerserves as a feeding layer, wherein said electroless plating unitincludes: a seal packing to be brought into contact with the substrate;a plating cell for forming a hermetically sealed space with thesubstrate and said seal packing, the hermetically sealed space having avolume sufficient for receiving a minimum amount of an electrolessplating liquid required for the electroless plating process; and aturntable for holding the substrate so that the substrate is cleaned anddried after the electroless plating process.
 2. An apparatus accordingto claim 1, wherein said transfer mechanism is linearly movable.
 3. Anapparatus according to claim 1, wherein said processing units alsoinclude a cleaning and drying device for cleaning and spin drying thesubstrate after the electrolytic plating process.
 4. An apparatusaccording to claim 1, wherein said processing units also include apretreatment unit for performing a pre-treatment process of theelectroless plating process.
 5. An apparatus according to claim 1,wherein said electrolytic plating unit comprises an electrolytic platingbath having a plating liquid comprising copper sulfate (CuSO₄.5H₂O)having a concentration of 100 to 250 g/l.
 6. An apparatus according toclaim 1, wherein said electrolytic plating unit comprises anelectrolytic plating bath having a plating liquid comprising sulfuricacid (H₂SO₄) having a concentration of 10 to 100 g/l.
 7. An apparatusaccording to claim 1, wherein said electrolytic plating unit comprisesan electrolytic plating bath having a plating liquid comprising chlorineions having a concentration of 0 to 100 mg/l.
 8. An apparatus accordingto claim 1, wherein said electrolytic plating unit comprises anelectrolytic plating bath having a plating liquid comprising at least0.14 to 70 μmol/l of a sulfur compound expressed by a formulaX—L—(S)_(n)—L—X where L is an alkyl group having a carbon number of 1 to6 which is substituted by a lower alkyl group, a lower alkoxyl group, ahydroxyl group, or a halogen atom; n is an integer; and X is a hydrogenatom, a —SO₃M group, or a —PO₃M group; and M indicates a hydrogen atom,an alkali metal atom, or an amino group.
 9. An apparatus according toclaim 1, wherein said electrolytic plating unit comprises anelectrolytic plating bath having a plating liquid comprising at least 10to 5000 mg/l of a macromolecular compound expressed in a formula

where R₁ indicates a residue of a higher alcohol group having a carbonnumber of 8 to 25, a residue of an alkyl phenol with an alkyl grouphaving a carbon number of 1 to 25, a residue of an alkyl naphthol withan alkyl group having a carbon number of 1 to 25, a residue of a fattyacid amide having a carbon number of 3 to 22, a residue of an alkylaminehaving a carbon number of 2 to 4, or a hydroxyl group; R₂ and R₃indicate a hydrogen atom or a methyl group; and m and k indicate aninteger from 1 to
 100. 10. An apparatus according to claim 1, whereinsaid electrolytic plating unit comprises an electrolytic plating bathhaving a plating liquid comprising at least 0.01 to 100 mg/l of anitrogen compound.
 11. An apparatus according to claim 1, wherein saidframe is rectangular in shape.
 12. An apparatus according to claim 1,wherein said electroless plating unit also includes a waste liquid tankfor receiving the electroless plating liquid that has been used for theelectroless plating process, without circulating the electroless platingliquid.
 13. An apparatus according to claim 1, wherein said electrolessplating unit further includes a cleaning nozzle for ejecting a cleaningliquid to a surface of the substrate to clean the substrate after theelectroless plating process.
 14. An apparatus according to claim 1,wherein said turntable is configured to be rotated at a high rate ofspeed to dry the substrate after the electroless plating process.